Oil field drilling operations utilizing a rotary drill string and having a section or sections of drill collar immediately above the drill bit require the application of a drilling stabilizer to the drill collar section or sections in order to minimize the seizure within the drill bore of the drill collar as well as to stabilize the drill string during drilling operations.
It is desired that a drilling stabilizer be quickly connected or disconnected to the drill collar, and that a minimum of manual operations be involved during the connecting or disconnecting of the stabilizer. It is further desirable to employ a drilling stabilizer which can be affixed to the collar section in such a manner that each stabilizer can be affixed at any desired interval from the preceeding stabilizer. Those familiar with oil field operations will recognize that the various combinations and spacings of drilling stabilizers are often determinative in obtaining a desired drilling result. It is also advantageous to utilize a drilling stabilizer which is durable throughout a particular drilling operation and which is readily adaptable to any number of dissimilar drill collars utilized in oil field operations around the world. One such drilling stabilizer which has frequently been used is described and claimed in U.S. Pat. No. 3,916,998 (hereinafter referred to as the 3,916,998 patent).
The drilling stabilizer described in the 3,916,998 patent comprises fundamentally a rigid main sleeve having an axial passageway extending therethrough and a rib midway of the passageway against each side which a pair of slideably received rings abut. An end cap is threadedly engaged into each end of the rigid main sleeve in such a manner that as the end cap is threaded into the sleeve the inner ring of a pair of rings is forcefully urged into a clamping engagement with the outer surface of the drill collar. Likewise, the outer ring is forced against the inner surface of the main sleeve. Consequently, the device in the 3,916,998 patent can be selectively applied to any location on a drilling collar. Moreover, since only the interior surface of the inner split ring contacts the drill collar, flexibility within the drill collar is not sacrificed by the application of numerous drilling stabilizers.
A shortcoming of the device in the 3,916,998 patent, however, has been that once the drilling stabilizer is successfully clamped onto the drill collar, it is frequently difficult to disengage and remove the stabilizer from the collar. Those familiar with drilling operations appreciate that mere removal of the end cap from the rigid main sleeve often does not disengage the outer split ring from the inner split ring on either or both pairs of rings. Consequently, although the end cap has been threadedly disengaged from the rigid main sleeve, the corresponding pair of split rings still exerts a force or forces clamping the stabilizer to the collar. A common practice for disengaging the stabilizer from the collar has been to strike the stabilizer forcefully with any suitable device such as a large hammer. Such an operation clearly requires additional manual effort, tools, time and is also destructive of the stabilizer itself.
The present invention is directed toward the elimination of the shortcomings of a drilling stabilizer similar to the one shown and described in the 3,916,998 patent. The present invention described and claimed hereinafter employs an annular rib and an annular groove on the interior surface of the outer split ring and an annular groove and annular rib on the exterior surface of the end cap whereby the rib of the outer ring is substantially disposed within the groove of the end cap and the rib of the end cap is substantially disposed within the groove of the outer ring. The outer ring is urged into engagement with the end clamp before threading the end cap into the main sleeve. The interaction between the groove and rib on the ring with the rib and groove respectively of the end cap produces a locking action in the axial direction. The result of the axial interlock configuration is that the outer split ring necessarily follows the end cap as the end cap is threadedly disengaged from the rigid main sleeve, thereby unclamping the pair of rings from the sleeve and drill collar. Those familiar with drilling operations will realize that as the second end cap is threadedly disengaged from the drilling stabilizer that the stabilizer itself can be axially moved along the drill collar for repositioning, engagement and disengagement with the collar.
It is an object of the present invention to provide a drilling stabilizer which is easily applied to and removed from a drill collar.
Another object of the present invention is to utilize a clamping means of the drill stabilizer which allows the stabilizer to remain clampingly fixed to the drill collar without unduly restricting the flexibility of the collar.
A still further object of the present invention is to provide a clamping means in the drilling stabilizer which, when actuated by the end cap effectively affixes the stabilizer to the drill collar, and upon disengagement of the end cap from the rigid main sleeve unclamps the clamping means thereby allowing the drilling stabilizer to be axially repositioned on or removed from the drill collar.
It is yet a further object of this invention to provide a clamping means on a drilling stabilizer which is effectively and automatically unclamped without applying shock forces to the drilling stabilizer or without the use of auxiliary tools other than those necessary to threadedly remove the end cap from the rigid main sleeve.
Further objects and other features and advantages of the present invention will be apparent in the following description of the preferred embodiments of the invention, given for the purpose of disclosure and taken in conjunction with the accompanying drawings.